Interspecific variations in leaf litter decomposition and nutrient release from tropical mangroves

Area of Science:

• Marine Ecology
• Biogeochemistry
• Mangrove Ecosystems

Background:

• Mangrove ecosystems are crucial for coastal productivity and carbon sequestration.
• Leaf litter decomposition is a key process regulating nutrient cycling and carbon export.

Purpose of the Study:

• To characterize mangrove leaf litter decomposition and its role in nutrient supply to coastal waters.
• To assess the potential of different mangrove species' leaf litter to support aquatic food webs and sequester carbon.

Main Methods:

• Controlled incubation experiments of leaf litter from four major mangrove species (A. officinalis, R. mucronata, H. littoralis, S. apetala).
• Measurement of decomposition rates (half-life time), organic carbon release (labile vs. recalcitrant), total heterotrophic bacterial (THB) populations, and Chromophoric Dissolved Organic Matter (CDOM).
• Estimation of annual litter fall and carbon content in the Bhitarkanika mangrove forest.

Main Results:

• Leaf litter decomposition half-life ranged from 18 to 52 days.
• S. apetala leaf litter released labile organic carbon supporting aquatic food webs, while R. mucronata released recalcitrant humic substances.
• Total heterotrophic bacterial populations increased significantly, with rapid carbon release observed between days 7 and 21 for S. apetala and R. mucronata, respectively.
• Estimated annual litter fall was 11.32 ± 1.57 Mg ha⁻¹ y⁻¹, with a carbon content of 5.43 ± 0.75 Mg C ha⁻¹.

Conclusions:

• Mangrove leaf litter leachates are a significant food source for coastal microbial communities.
• Leaf litter plays a dual role in carbon sequestration through soil burial and export to the deep sea.
• Species-specific litter characteristics influence nutrient cycling and carbon dynamics in coastal waters.